Heating systems and elements of a wide variety of types are already known. For domestic and industrial heating purposes, most of the systems in wide usage either employ open flame gas burners or electrical resistance heating elements. For example, kitchen ranges are customarily provided either with a group of open flame gas burners, or with a group of flat coil electrical heating elements.
Open flame gas burners have certain advantages including the fact that the burner may readily be incrementally adjusted to the flame or heat desired, but open flame burners have serious disadvantages including the release of noxious fumes and the tendency to accumulate soot in surrounding areas. Open flame burners also present an explosion hazard. In addition, they tend to produce excessive heat in the working area and result also in burning up of the oxygen in the working area. Still further the open flame burners are disadvantageous as they require either matches or a constantly burning pilot light for ignition. Moreover, in spite of the fact that the common gas supply systems operate at a pressure of only a minor fraction of 1 psi, any leak in the system is a potential fire hazard because the leakage gas may readily be ignited in the presence of the oxygen in the ambient air.
On the other hand the common electrical resistance heating elements are advantageous in that they eliminate some of the deficiencies just referred to of open flame gas burners. However, the electrical heating resistance elements are in general more expensive to operate than those operating with gas, this differential being very pronounced in certain areas of the United States and many other countries, notably those areas which are relatively accessible to sources of natural gas in which one cent will buy about four times as many Btu with gas as with electricity.
Both electric and open flame gas burners also have the disadvantage that the heating rate with such burners is relatively low.